A prior-art device for obtaining wavelength-resolved images is described in Patent Publication No. 2,558,864 by this applicant. With this device, a sample is illuminated uniformly from the rear side, an image of the transmitted light that has been transmitted through the sample is formed on a slit plate, a galvanomirror is used to scan the transmitted light image that is projected onto the slit plate and thereby cut out a slit image, this slit image is subject to spectral resolution, and spectrally resolved images are captured by a TV camera. Images captured by the TV camera are synthesized as sample images according to wavelength.